The present invention relates generally to radio frequency identification (RFID) systems, and more particularly to apparatus for evaluating radio fequency identification systems.
Radio frequency identification (REID) systems are known systems which allow objects to be labeled with tags such that when the tag is passed through the electromagnetic field of a reader/interrogator the object is identified by reading the tag attached to he object.
The tag includes an antenna, which may be a dipole for far field systems or a coil for inductive systems tuned to the frequency of the interrogator""s generated electromagnetic field. The electrical current generated in the tag""s antenna powers the tag. Data is generally sent to the tag by modulating the interrogator generated electromagnetic field which is commonly called the exciter or illuminating field. The tag sends data back to the interrogator either by transmitting with its own transmitter with a separate frequency and antenna from the illuminating field or by modulating the illuminating field by changing the loading of the tag""s antenna in what is commonly called a back scatter system. In any case, either the new electromagnetic field from the tag or the disturbances in the interrogator""s illuminating field caused by the tag""s back scatter system is detected by the interrogator. The data from the tag is decoded, thereby enabling the tag and the item to which the tag is attached to be identified. In some cases the tag is written to, as in the case of read/write tags, by modulating the interrogator""s generated electromagnetic field. Typical information that might be stored on the tags includes: purchase order number (i.e. PO#); expire date; destination; confirmation of an applied process, etc.
With a RFID system, or other types of wireless installations, the location for the installation must be checked for suitability. This is especially true for automated RFID tag systems since the tags are generally mounted on objects that are being moved through the interrogation field of a reader which is fixed. The other possibility is where the tagged objects are not moving i.e. on storage shelves, and the reader is moving, for example the reader is mounted on a forklift. In either case the dynamics between the reader and the tags are changing and it is difficult to characterize the coverage of the RF field, because of interference to other equipment and interference from other equipment.
One known method for evaluating a site and tag equipment involves using test equipment to characterize existing radiation at the site and mapping the power levels from the tag equipment. While this testing procedure does provide good diagnostic information for determining causes of problems with existing installations, there are a number of shortcomings. The principal problem with this approach is that the test equipment required to perform, the evaluation is expensive and requires a very skilled and experienced technician. It is also difficult and inaccurate to convert these results into appropriate range and accuracy figures for the operation of the RFID system. Furthermore, the results are not representative of actual operating conditions with moving tags and readers.
A second known method in the art involves installing a pilot system and allowing the system to operate for a period of time all the while collecting statistical data on its performance. While this approach produces actual operating conditions, it is expensive in terms of equipment, is logistically difficult to set,o, and is slow to produce results. It is generally considered a xe2x80x9cgo/no goxe2x80x9d type of evaluation and must be run for a very long time collecting statistics in order to characterize any marginal conditions. It ""s therefore not useful for determining actual installation positions or for diagnosing the reasons why a site is good or bad.
In view of the shortcomings with the prior art techniques, there still remains a need for RFID survey tools and techniques.
The present invention provides an apparatus and method for evaluating and installing a wireless system and is Particularly suited to radio fequency identification (RFID) systems. The tag evaluation apparatus and method determine the suitability of a particular site for use with specific identification tag types. The tag evaluation apparatus may be utilized before installation as a site survey tool or after installation as a diagnostic or performance optimizing toot.
In accordance with the present invention, the power levels on actual tags are measured for the communications in and out of the tags and are compared with the communications from the interrogator. The RFID tag evaluation apparatus provides the capability or different tag types to be evaluated in actual use on the items to be tagged while the tag item (or tag items) is being transported in the operational mode. The RFID tag evaluation module measures and records the key parameters for operation of an RFID tag system in real-time, and is capable of highlighting marginal areas. As such, the system is suitable for evaluating and determining antenna placements and diagnosis of existing systems.
In a first aspect, the present invention provides apparatus for evaluating a radio frequency identification system having a plurality of tags, said tags operating at a selected frequency, and said tags being responsive to an output signal transmitted by an interrogator and including a circuit for receiving the output signal transmitted by the interrogator and transmitting a return signal in response to said output signal, said evaluation apparatus comprising: (a) a probe for coupling to the circuit in one of said tags, and said probe including a plurality of lines for sampling selected signals in said circuit; (b) a controller coupled to said probe and including a processor for processing said sampled signals and memory for storing information associated with said sampled signals; and (c) a transmitter coupled to said controller and responsive to control signals from said controller for transmitting said stored information to a remote device, wherein said transmitter utilizes a communication channel operating at a different frequency than the selected frequency for the tags.
In another aspect, the present invention provides apparatus for evaluating a wireless system having a plurality of wireless terminals, the wireless terminals operate at a selected frequency, and the wireless terminals are responsive to an output signal transmitted by a transceiver terminal and each of the wireless terminals includes a circuit for receiving the output signal transmitted by the transceiver terminal and transmitting a return signal in response to the output signal, the apparatus comprises: (a) a probe for coupling to the circuit in one of the wireless terminals, and the probe includes a plurality of lines for sampling selected signals in the circuit; (b) a controller is coupled to the probe and includes a processor for processing the sampled signals and memory for storing information associated with the sampled signals; and (c) a transmitter is coupled to the controller and is responsive to control signals from the controller for transmitting the stored information to a remote device, wherein the transmitter utilizes a communication channel operating at a different frequency than the selected frequency for the wireless terminal.
In yet another aspect, the present invention provides a data signal embodied in a carrier wave, the data signal provides information from a tag under evaluation in a radio frequency identification system to a remote device, the radio frequency identification system includes a plurality of tags operating at a selected frequency, and the tags are responsive to an output signal transmitted by an interrogator, the data signal comprises: (a) an envelope; (b) a data portion, the data portion provides information about the tag under evaluation.